An integrated circuit is generally fabricated utilizing a chip of silicon or other semiconductor material, also referred to as a die. A die is typically installed in a package, and electrically connected to leads of the package. These leads may then be soldered to traces on a printed wiring board (PWB), or other circuit mounting structure, to provide connections between the die and external circuitry.
A number of different cavity packages are known in the art, and may be used, by way of example, to package a Radio Frequency Laterally Diffused Metal Oxide Semiconductor (RFLDMOS) device or other integrated circuit device. In one type of cavity package, a die is sealed inside a protective enclosure. Leads penetrate the walls of the protective enclosure so that they may be electrically connected to the die. These packages are known in the electronics industry as “air-cavity packages,” since the die resides in a hollow air-filled cavity inside the enclosure.
A cavity package dissipates heat, which the die generates during use, through the floor, or heat spreader, of the package. For this reason a heat-conductive material, generally a metal plate, is used as the heat spreader. A high-temperature, heat-conductive solder joins the die to the heat spreader. Packages are generally formed by bonding sidewalls, having leads passing through them, to the heat spreader to form the body of the package. Once the body is formed, the die is placed inside the body and secured to the heat spreader. Wire bonding is performed to join the die circuitry to the leads, and the package is completed by securing a lid to the body with an appropriate adhesive. Examples of cavity packages and associated packaging methods are described in U.S. Patent Application Publication No. US 2003/0013234 A1 to Bregante et al. and U.S. Patent Application Publication No. US 2003/0085464 A1 to Lang.
A high soldering temperature (e.g., 400° C.) is typically needed to secure the die to the heat spreader of the cavity package. The sidewalls of the package therefore must be constructed of a material that can withstand the high temperature. For this reason, cavity package sidewalls and lids may be constructed of a ceramic material. However, the ceramic materials used are expensive. Manufacturing costs can be reduced considerably if the ceramic materials are replaced by plastic materials, but plastics do not readily withstand the high soldering temperature, and the manufacturing process must therefore be altered. Further, while plastic and overmolded plastic cavity packages incorporate less expensive materials than ceramic packages, their processing and tooling may be expensive. Finally, seals created on the plastic package are generally less reliable than those created on the ceramic package due to moisture diffusion through the plastic.
Conventional cavity packages of the type described above typically require that any additional circuit components, including signal filters, tuning capacitors and inductors, be mounted inside the cavity of the package or on the PWB outside the package. These cavity packages may also require external shielding in high frequency applications.
Thus, a need exists for an integrated circuit device that may be manufactured inexpensively while being versatile in incorporating additional circuit components and shielding within the integrated circuit device.